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The archive is a reconstruction of past weather on a 9–25 km grid, not a station in your street. Thin snow, mountains and coasts can differ from what you saw. That is why answers are counted over seasons, with a margin.

There are two honest reasons, and the app cannot tell you which one applies. The first is memory: a few vivid winters tend to stand in for all of them. Measuring that is what the app is for.

The second is the archive. It is a reanalysis: past weather reconstructed on a grid of 9 to 25 kilometres. It does not come from a station in your street. In the mountains, on a coast or in a valley, and especially for a thin layer of snow on one day, the grid cell and your garden can differ. That is why questions are counted over whole seasons, numeric answers get a margin of about a tenth of the scale, and every result says “in the archive”.

A hatched year sits on the edge: the archive holds one to three centimetres of snow that day. It counts as right whichever way you answered.

A hatched year sits on the edge. The app calls a day a day of snow when the archive shows at least 2 cm on the ground on average that day. Between 1 and 3 cm it is treated as borderline: the year is drawn hatched and counted as a match whichever way you answered.

Hot days are normally counted from a daily maximum of 30 °C. In towns where a typical summer has fewer than three such days, every question would have the answer “none”. There the app counts from 25 °C instead, and the question says which threshold is in use. The other thresholds are the same everywhere: a frost day has a minimum below 0 °C, a rainy day has at least 1 mm, and first snow is at least 1 cm falling in a day. They are all listed in Settings under the data source.

Because it is about the past and nothing else. It shows no current conditions and no outlook for coming days. The archive itself trails today by about a week, so the most recent date you can open is roughly seven days ago.

Any date from 1 January 1940 up to about a week ago, for any town the search can find, anywhere in the world. If your childhood began before 1940, the app uses the years that are available; if fewer than three remain, it starts with your youth or with the earliest seven years on record.

In places where snow never settles, the snow questions are asked once at most and the app concentrates on frost, summer and rain.

Each counted answer is compared with the archive and the difference is kept with its sign: did you remember more or less than was there? The drift for an axis (winter, summer or rain) is the average of your last twelve answers on it, shown as a percentage once you have at least three. Under 8% either way, the app says memory and archive nearly agree. Pick-one questions, such as which of two winters was snowier, are recorded as matched or not matched and do not move the drift.

On the Horizon or in the Album, choose “A day from the archive”, then a date, a town and an optional caption. You can say how you remember the day (sky, rain or snow, warmth) or skip that. The day then plays back in 20 seconds; drag across the scene to move through the hours. With Reduce Motion switched on in iOS, the playback becomes four still frames.

“Keep in the album” stores the day; the album holds up to 200. A kept day can be saved as an image through the share sheet. What you remembered about a single day is compared on its card only and does not change your drift.

Only on this phone, in the app’s own storage. Nothing is uploaded and there is no account, so deleting the app removes them and a new phone starts empty.

Settings → Erase everything removes your years, towns, answers and album from this phone and takes you back to the start. It cannot be undone.

Settings → Stretches of your life adds up to five periods, each with its own town. Where you live now and Birthday are in Settings too. To change the birth year, erase everything and start again.

Partly. A connection is needed to search for a town, to open the archive for a new stretch of years and to open a new day. Everything already downloaded keeps working without one: the Horizon, your settled disputes, new questions for stretches already loaded, and every kept day in the album.

No and no. There is no sign-up, no login, no subscription, no purchase and no advertising. The app also asks for no access to your location, camera, microphone or photo library. The only system prompt you may see is the one for notifications.

For the weather: the town name you type, the rounded coordinates of the town you choose and a range of dates, all to Open-Meteo. Your birth year, birthday, answers and album are never sent.

Apart from that: a check at launch that the app is up to date (app version, bundle identifier and an installation identifier), push notifications through OneSignal if you allow them, and your help desk message when you press Send. The privacy policy lists every field.

Years you already opened work without a connection. A new stretch of your life, a new town or a new day needs the network once. Check the connection and tap Try again; if the archive is busy, give it a minute.

Check that the iPhone is online and tap “Try again”. The app retries a few times by itself. If the message says the archive is busy, the data service is limiting requests for a moment; wait a minute and try again. Opening a new stretch of seven years takes several requests in a row, so on a slow connection the sky rewind can run for a while.

Type at least two letters and wait a moment. Try the name in the local language or in English, without the region. Very small villages may be missing from the place database; choose the nearest town, which usually falls in the same or a neighbouring grid cell of the archive anyway.

Everything is stored on the phone only, and the app keeps no copy on a server. Deleting the app, or using “Erase everything”, removes it for good and we cannot bring it back. If you restore the iPhone from a device backup made earlier, the app’s data usually comes back with it. To keep a particular day safe, save its card as an image.

Open the iOS Settings app, choose Notifications, then Neve Vesper, and check that Allow Notifications is on. A Focus mode or Low Power Mode can hold notifications back. The app sends few of them, only about the app itself. To stop them, switch the same setting off.

If the archive returns no value for a year at your location, that year is left out so that you are not asked something that cannot be checked. If too few years remain, that kind of question is not asked for that stretch.